Radiation imaging system, radiation imaging apparatus, and method of controlling the same

ABSTRACT

User-friendliness of a radiation imaging apparatus configured to reset a sensor array is improved. This invention is a radiation imaging apparatus including a two-dimensional sensor array. This apparatus includes a scan control signal generation circuit which controls the reset operation of the two-dimensional sensor array, a row number register which stores the row number of a line currently subjected to the reset operation at the time of detection of radiation irradiation, a scan control signal generation circuit which controls read operation after the completion of the radiation irradiation, and an image processing circuit which interpolates an image, of the image generated based on the signals read by the read operation, which corresponds to a line corresponding to the row number stored in the row number register, by using images of adjacent lines.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to a radiation imaging system, aradiation imaging apparatus, and a method of controlling the same.

Description of the Related Art

There has been a flat panel type radiation imaging apparatus providedwith a sensor array formed by two-dimensionally arraying a plurality ofpixels. Each pixel used for such a radiation imaging apparatus generallyincludes a conversion element which is obtained by forming a film on aglass substrate by using amorphous silicon or polysilicon as a materialand converts radiation into an electrical signal and a switch elementsuch as a TFT for transferring the electrical signal to the outside. Ingeneral, such a radiation imaging apparatus performs read operation bytransferring, to a reading apparatus, the signals converted byconversion elements upon performing matrix driving using switch elementssuch as TFTs.

Each conversion element on the sensor array directly or indirectlygenerates a signal upon being irradiated with radiation. In a sensorarray configured to indirectly generate signals, the conversion elementof each pixel detects visible light converted from radiation by aphosphor instead of directly detecting radiation. In a sensor arraybased on either the direct detection scheme or the indirect detectionscheme, each pixel generates a signal with a certain level even in thetotal absence of radiation. In this case, this signal will be referredto as a “dark current”.

Dark currents have different characteristics in the respective pixels onthe sensor array. If dark currents are superimposed on the image signalsobtained by radiation irradiation, uneven offsets are added to an image,resulting in a deterioration in image quality. In order to prevent this,the radiation imaging apparatus is configured to extract dark currentcharges from the sensor array periodically and/or intensivelyimmediately before radiation irradiation by using a period during whichno radiation is irradiated.

In this case, when extracting a dark current, if an image signal issuperimposed on the dark current, it is not possible to separate themand extract only the dark current. That is, executing dark currentextraction during radiation irradiation or in the interval afterradiation irradiation and before reading of an image signal will losethe image signal. Therefore, in the radiation imaging apparatus, it isnecessary to perform control so as to exclusively execute dark currentextraction and radiation irradiation. For this reason, a synchronizationmechanism for establishing synchronization is provided between theapparatus and a radiation source.

Depending on the scheme, some conversion element needs to periodicallyperform reset operation as well as dark current extraction. In this caseas well, reset operation leads to the loss of an image signal, andrequires exclusive control with respect to radiation irradiation.

SUMMARY OF THE INVENTION

The radiation imaging apparatus according to the embodiment of thepresent invention has the following arrangement. That is, a radiationimaging apparatus including a sensor array, comprising: first controlunit configured to control reset operation of sequentially removingsignals respectively output from a plurality of lines constituting thesensor array; identifying unit configured to identify a line currentlysubjected to the reset operation when a start of radiation irradiationis detected; second control unit configured to control read operation ofreading a signal output from each of the plurality of lines at a timingset in advance for each line upon completion of the radiationirradiation; and interpolation unit configured to interpolate an image,which is part of an image generated based on signals read by the readoperation, and which corresponds to a line identified by the identifyingunit, by using images of adjacent lines.

In addition, another radiation imaging apparatus according to theembodiment of the present invention has, for example, the followingarrangement. That is, a radiation imaging apparatus including a sensorarray, comprising: control unit configured to sequentially read signalsrespectively output from a plurality of lines constituting the sensorarray; identifying unit configured to identify a line currentlysubjected to the read operation when a start of radiation irradiation isdetected; and interpolation unit configured to interpolate an image,which is part of an image generated based on signals read by the controlunit after completion of the radiation irradiation, and whichcorresponds to a line identified by the identifying unit, by usingimages of adjacent lines.

A method of controlling a radiation imaging apparatus according to theembodiment of the present invention has, for example, the followingarrangement. That is, a method of controlling a radiation imagingapparatus including a sensor array, comprising: a first control step ofcontrolling reset operation of sequentially removing signalsrespectively output from a plurality of lines constituting the sensorarray; an identifying step of identifying a line currently subjected tothe reset operation when a start of radiation irradiation is detected; asecond control step of controlling read operation of reading a signaloutput from each of the plurality of lines at a timing set in advancefor each line upon completion of the radiation irradiation; and aninterpolation step of interpolating an image, which is part of an imagegenerated based on signals read by the read operation, and whichcorresponds to a line identified in identifying step, by using images ofadjacent lines.

Further features of the embodiment of the present invention will becomeapparent from the following description of exemplary embodiments (withreference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theembodiments of the invention.

FIG. 1 is a block diagram showing the arrangement of a radiation imagingapparatus 100;

FIG. 2 is a flowchart showing a procedure for imaging processing by theradiation imaging apparatus 100;

FIG. 3 is a timing chart showing a procedure for imaging processing bythe radiation imaging apparatus 100;

FIG. 4 is a view for explaining image interpolation processing by animage processing circuit 133;

FIG. 5 is a flowchart showing a procedure for imaging processing by theradiation imaging apparatus 100;

FIG. 6 is a timing chart showing a procedure for imaging processing bythe radiation imaging apparatus 100;

FIG. 7 is a view for explaining image interpolation processing by theimage processing circuit 133;

FIG. 8 is a timing chart for explanation in contrast with FIG. 6;

FIG. 9 is a view for explanation in contrast with FIG. 7;

FIG. 10A is a flowchart showing a procedure for imaging processing bythe radiation imaging apparatus 100;

FIG. 10B is a flowchart showing a procedure for imaging processing bythe radiation imaging apparatus 100;

FIG. 11 is a timing chart showing a procedure for imaging processing bythe radiation imaging apparatus 100;

FIG. 12 is a timing chart showing a procedure for imaging processing bythe radiation imaging apparatus 100;

FIG. 13 is a block diagram showing the arrangement of a radiationimaging apparatus 1300;

FIG. 14A is a flowchart showing a procedure for imaging processing bythe radiation imaging apparatus 1300;

FIG. 14B is a flowchart showing a procedure for imaging processing bythe radiation imaging apparatus 1300;

FIG. 15 is a timing chart showing a procedure for imaging processing bythe radiation imaging apparatus 1300;

FIG. 16 is a timing chart showing a procedure for imaging processing bythe radiation imaging apparatus 1300;

FIG. 17 is a view showing the arrangement of a two-dimensional sensorarray and its peripheral circuit;

FIG. 18 is a view showing an example of the structure of a shiftregister 122;

FIG. 19 is a timing chart for explaining a control method for the shiftregister 122;

FIG. 20 is a timing chart for explaining the operation of the shiftregister 122; and

FIG. 21 is a timing chart for explaining a control method for the shiftregister 122.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will now be described in detail inaccordance with the accompanying drawings.

First Embodiment 1. Arrangement of Radiation Imaging Apparatus

The arrangement of a radiation imaging apparatus according to the firstembodiment of the present invention will be described first. FIG. 1 is ablock diagram showing the arrangement of a radiation imaging apparatus100 according to this embodiment. As shown in FIG. 1, the radiationimaging apparatus 100 includes a two-dimensional sensor array 121 as areceiver. A shift register 122 as a row selection means is connected tothe two-dimensional sensor array 121. The shift register 122sequentially selects the TFT switches on the two-dimensional sensorarray 121 to scan the two-dimensional sensor array 121. Column signallines connecting the respective column pixels are wired on thetwo-dimensional sensor array and are connected to a charge amplifier123. It is possible to generate an image by measuring signals (chargeamounts) flowing in the respective column signal lines using the chargeamplifier while scanning the two-dimensional sensor array 121.Performing scanning while fixing the voltage of each column signal lineto a specific value can perform the reset operation of removing darkcurrents.

The radiation imaging apparatus 100 is further equipped with an ASIC130. A scan control signal generation circuit 131 in the ASIC 130controls a sensor unit including the shift register 122 and the chargeamplifier 123. The scan control signal generation circuit 131 includes arow number register 132 which stores row numbers. When reset operationis interrupted at an arbitrary timing, the row number register 132 canstore the corresponding row number. When performing read operation, theapparatus starts the read operation from the line corresponding to a rownumber next to the row number stored in the row number register 132.After the read operation, the stored row number is transferred to animage processing circuit 133. In this manner, the scan control signalgeneration circuit 131 functions as the first control means forcontrolling reset operation and the second control means for controllingread operation.

An ADC (A/D Converter) 124 is connected to the charge amplifier 123.When performing read operation, the apparatus converts a signal (chargeamount) on each column signal line measured by the charge amplifier 123into a pixel digital value. The pixel digital value is transferred to aRAM 140 via a DMA controller 134 in the ASIC. Assume that when the DMAcontroller 134 transfers the pixel digital value onto the RAM 140, theapparatus has already adjusted the corresponding address upon receptionof a command from the scan control signal generation circuit 131. Pixeldigital values are arranged in the RAM 140 so as to reproduce the pixelarrangement on the two-dimensional sensor array.

The image processing circuit 133 in the ASIC 130 reads and computes thepixel digital values in the RAM 140. At this time, the image processingcircuit 133 refers to the row number stored in the row number register132 in the scan control signal generation circuit 131 described aboveand performs image interpolation processing concerning the linecorresponding to the row number.

The radiation imaging apparatus 100 is further equipped with an X-raydetector 110 separately from the above sensor unit. This allowsdetection of the start and stop of X-ray irradiation. An output from theX-ray detector 110 is input to the ASIC 130. The scan control signalgeneration circuit 131 can identify an X-ray irradiation state.

2. Operation of Radiation Imaging Apparatus

The operation of the radiation imaging apparatus 100 will be describednext with reference to FIGS. 2 to 4. FIG. 2 is a flowchart showing aprocedure for imaging processing by the radiation imaging apparatus 100.FIG. 3 is a timing chart for the procedure. FIG. 4 is a view forexplaining image interpolation processing by the image processingcircuit 133.

As shown in FIG. 2, when starting imaging processing, the apparatusstarts the reset operation of the two-dimensional sensor array 121 instep S201. When starting reset operation, the apparatus performs thereset operation from the line corresponding to row number=1, as shown inFIG. 3, under the control of the shift register 122. Upon completing thereset operation up to the line corresponding to row number=10, theapparatus performs reset operation again from the line corresponding torow number=1.

During this period, the apparatus determines in step S202 whether theX-ray detector 110 has detected X-ray irradiation. If NO in step S202,the apparatus stands by until X-ray irradiation is detected. If YES instep S202, the process advances to step S203 to stop reset operation.

In step S204, the row number register 132 stores the row number of theline on which reset operation has been executed at the time of stop ofreset operation. In step S205, the apparatus determines based on anoutput from the X-ray detector 110 whether X-ray irradiation iscomplete. If the apparatus determines that X-ray irradiation iscomplete, the process advances to step S206.

FIG. 3 exemplifies how the user performs operation to start X-rayirradiation when the apparatus is executing reset operation on the linecorresponding to row number=6, and the X-ray source performs X-rayirradiation simultaneously with the operation. As shown in FIG. 3, theradiation imaging apparatus 100 according to this embodiment stops resetoperation immediately after the detection of X-ray irradiation,sequentially starts read operation from the line corresponding to rownumber=1 upon detection of the completion of X-ray irradiation, andstores each pixel digital value in the RAM 140.

In step S207, the apparatus performs image interpolation processing fora value, of the pixel digital values stored in the RAM 140, whichconcerns the line corresponding to the row number stored in the rownumber register 132 by using the lines corresponding to the precedingand succeeding row numbers (that is, pixel digital values on theadjacent lines).

Referring to FIG. 4, reference numeral 401 denotes an X-ray imagegenerated based on each pixel digital value stored in the RAM 140. Asshown in FIG. 4, the X-ray image 401 lacks in a pixel digital value onthe line corresponding to row number=6 because X-ray irradiation isperformed during the execution of reset operation on the line. Referringto FIG. 4, reference numeral 402 denotes an X-ray image obtained byperforming image interpolation processing for the X-ray image 401 by theimage processing circuit 133. As shown in FIG. 4, since the X-ray image402 is obtained by interpolating the pixel digital value on the linecorresponding to row number=6 by the pixel digital values on thepreceding and succeeding row numbers (for example, row number=5 and rownumber=7), it is possible to suppress a deterioration in image quality.

When the image processing circuit 133 completes the above imageinterpolation processing, the apparatus determines in step S208 whetherthe imaging processing is complete. If NO in step S208, the processreturns to step S201, in which the apparatus starts reset operationagain. If the apparatus has received an end instruction from the userand determines to terminate the processing, the apparatus terminates theimaging processing.

As is obvious from the above description, the radiation imagingapparatus 100 according to this embodiment is configured to stop resetoperation simultaneously with the detection of X-ray irradiation. Thismakes it possible to eliminate the delay time between the instant theuser performs operation to start X-ray irradiation and the instantradiation is actually irradiated. That is, it is possible to eliminatethe time lag between user's operation for radiation irradiation andimaging operation, thereby improving the user-friendliness.

In addition, the radiation imaging apparatus 100 according to thisembodiment is configured to store the row number of the line on whichreset operation has been executed at the time of stop of the resetoperation and interpolate the line corresponding to the stored rownumber by using the pixel digital values on the lines corresponding toother row numbers. This makes it possible to suppress a deterioration inimage quality caused by the deficiency of the pixel digital value on theline corresponding to the above row number.

The radiation imaging apparatus 100 according to this embodiment neednot recognize the timing of X-ray irradiation in advance as long as theX-ray detector 110 can detect X-ray irradiation. This makes itunnecessary to perform communication between the X-ray source and theradiation imaging apparatus. This allows free handling of the radiationimaging apparatus, thereby improving the user-friendliness.

Second Embodiment

The first embodiment has exemplified the case in which reset operationis performed line by line. However, the present invention is not limitedto this, and can also be applied to a case in which reset operation issimultaneously performed on a plurality of lines (at least some of resetoperation timings overlap between a plurality of lines).

When simultaneously performing reset operation on a plurality of lines,if the apparatus is configured to simultaneously perform reset operationon a plurality of lines corresponding to consecutive row numbers, theapparatus cannot make an image processing circuit 133 execute imageinterpolation processing. For this reason, a radiation imaging apparatus100 according to this embodiment is configured to distribute a pluralityof lines to be simultaneously subjected to reset operation. Theoperation of the radiation imaging apparatus 100 according to theembodiment will be described in detail below with reference to FIGS. 5to 9. Note that the following description will be mainly focused ondifferences from the first embodiment.

FIG. 5 is a flowchart showing a procedure for imaging processing by theradiation imaging apparatus 100 according to this embodiment. FIGS. 6 to9 are timing charts at the time of imaging processing and views forexplaining image interpolation processing. Note that FIGS. 6 and 7 showa case in which the apparatus simultaneously performs reset operation ona plurality of lines corresponding to distributed row numbers. Forcomparison, FIGS. 8 and 9 show a case in which the apparatussimultaneously performs reset operation on a plurality of linescorresponding to consecutive row numbers.

As shown in FIG. 5, when starting imaging processing, the apparatusstarts reset operation on a two-dimensional sensor array 121 in stepS201. In this embodiment, when starting reset operation, the apparatussequentially performs reset operation in the order of row numbers=1, 3,5, 7, 9, 2, 4, 6, 8, and 10, as shown in FIG. 6, under the control of ashift register 122. At this time, the shift register 122 performscontrol to simultaneously perform reset operation on lines correspondingto a plurality of row numbers (at least some of reset operation timingsoverlap between a plurality of lines). Note that the timing chart shownin FIG. 8 shows a case in which the apparatus performs control for resetoperation in accordance with an operation sequence, for example,starting from row number=1.

Upon determining in step S202 that X-ray irradiation has been detected,the apparatus stops reset operation in step S203. In step S204, a rownumber register 132 stores the row numbers of a plurality of lines onwhich reset operation has been executed at the time of stop of resetoperation.

In the case shown in FIG. 6, since the apparatus has performed X-rayirradiation while executing reset operation on the lines correspondingto row numbers=2, 7, and 9, the corresponding row numbers are stored. Inthe case shown in FIG. 8, since the apparatus has performed X-rayirradiation while executing reset operation on the lines correspondingto row numbers=4, 5, and 6, the corresponding row numbers are stored.

In step S205, the apparatus determines, based on an output from an X-raydetector 110, whether X-ray irradiation has been complete. If theapparatus determines that X-ray irradiation has been complete, theprocess advances to step S206 to perform read operation.

In the cases shown in FIGS. 6 and 8, the apparatus sequentially performsread operation from row number=1 in accordance with a reset operationsequence. That is, in the case shown in FIG. 6, the apparatussequentially performs read operation in the order of row numbers=1, 3,5, 7, 9, 2, 4, 6, 8, and 10, and stores the respective pixel digitalvalues in a RAM 140. In the case shown in FIG. 8, the apparatussequentially performs read operation in the order of row numbers=1, 2,3, . . . , 10, and stores the respective pixel digital values in a RAM140.

In step S207, the apparatus performs image interpolation processing forthe line corresponding to the first row number, of the plurality of rownumbers stored in the row number register 132, to which the respectivepixel digital values stored in the RAM 140 correspond, by using thelines corresponding to the preceding and succeeding row numbers of thefirst row number.

In step S501, the apparatus determines whether it has executed imageinterpolation processing for the lines corresponding to all the rownumbers stored in the row number register 132. If the apparatusdetermines in step S501 that the row numbers stored in the row numberregister 132 include the row number of a line for which imageinterpolation processing has not yet been executed, the process returnsto step S207. If the apparatus determines in step S501 that it hasexecuted image interpolation processing for the lines corresponding toall the row numbers, the process advances to step S208.

Referring to FIG. 7, reference numeral 701 denotes an X-ray imagegenerated based on each pixel digital value stored in the RAM 140. Asshown in FIG. 7, the X-ray image 701 lacks in pixel digital values onthe lines corresponding to row numbers=2, 7, and 9. Referring to FIG. 7,reference numeral 702 denotes an X-ray image obtained by performingimage interpolation processing for the X-ray image 701 in the imageprocessing circuit 133. As shown in FIG. 7, the apparatus interpolatesthe pixel digital value on the line corresponding to row number=2 byusing the pixel digital values on the lines corresponding to thepreceding and succeeding row numbers (for example, row number=1 and rownumber=3 for row number=2), it is possible to suppress a deteriorationin the image quality of the X-ray image 702.

Referring to FIG. 9, reference numeral 901 denotes an X-ray imagegenerated based on each pixel digital value stored in the RAM 140. Asshown in FIG. 9, the X-ray image 901 lacks in the pixel digital valueson the lines corresponding to row numbers=4, 5, and 6. In the case shownin FIG. 9, when the image processing circuit 133 performs imageinterpolation processing for the X-ray image 901, no pixel digitalvalues may exist at the preceding and succeeding row numbers. Forexample, with regard to row number=5, since the image lacks in pixeldigital values on the lines corresponding to the preceding andsucceeding row numbers (row number=4 and row number=6), the apparatuscannot perform image interpolation processing. For this reason, theapparatus cannot improve the image quality of an X-ray image 902 byimage interpolation processing. When simultaneously performing resetoperation on a plurality of lines, if the apparatus is configured tosimultaneously perform reset operation on a plurality of linescorresponding to consecutive row numbers, the image qualitydeteriorates.

As is obvious from the above description, the radiation imagingapparatus 100 according to this embodiment is configured tosimultaneously perform reset operation on a plurality of lines. Inaddition, the apparatus is configured to distribute a plurality of lineswhen simultaneously performing reset operation.

This makes it possible to suppress a deterioration in image quality evenwhen simultaneously performing reset operation on a plurality of lines.

Third Embodiment

The first and second embodiments have exemplified the case in which thenumber of lines of the two-dimensional sensor array is 10. Obviously,however, the present invention is not limited to this and can be equallyapplied to a two-dimensional sensor array including 11 or more lines.

In the second embodiment, the number of lines to be simultaneouslysubjected to reset operation is three. However, the present invention isnot limited to this. In general, the time for reset operation per lineis longer than that for read operation per line. It is thereforepreferable to decide the number of lines to be simultaneously subjectedto reset operation so as to make the number of lines to be subjected toreset operation per unit time coincide with the number of lines to besubjected to read operation per unit time.

If, for example, the number of lines to be subjected to reset operationper unit time is 1/S (S is an integer) of the number of lines to besubjected to read operation per unit time, it is preferable to decidethe number of lines to be simultaneously subjected to reset operation as“S”.

In the second embodiment, when distributing a plurality of lines to besimultaneously subjected to reset operation, the reset operationsequence is set to row numbers=1, 3, 5, 7, 9, 2, 4, 6, 8, and 10. Thatis, the apparatus is configured to perform reset operation, with rownumbers increasing by twos (one line skipping). However, the presentinvention is not limited to this, and may be configured to decide, forexample, the number of lines to be skipped in association with thenumber of lines to be simultaneously subjected to reset operation.

More specifically, letting N (N is an integer) be the number of lines ofthe two-dimensional sensor array and S be the number of lines to besimultaneously subjected to reset operation, the apparatus may beconfigured to decide a reset operation sequence such that row numbersincrease by n=N/S at a time. In this case, the apparatus performs resetoperation every n lines.

Fourth Embodiment

In the first to third embodiments, when starting read operation, theapparatus performs read operation from the line corresponding to rownumber=1 regardless of the row number stored in the row number register132. However, the present invention is not limited to this.

For example, the apparatus may be configured to perform read operationfrom the line corresponding to the row number next to the row numberstored in the row number register 132 (the line next to the line onwhich reset operation has been executed at the start of X-rayirradiation). This is because this arrangement allows keeping of theoperation intervals on the respective lines constant in the intervalfrom reset operation to read operation.

The operation of a radiation imaging apparatus 100 according to thisembodiment will be described below with reference to FIGS. 10A to 12.

FIGS. 10A and 10B are flowcharts showing a procedure for imagingprocessing by the radiation imaging apparatus 100 according to thefourth embodiment of the present invention. FIG. 11 is a timing chartfor a case in which the apparatus executes reset operation for eachline. FIG. 12 is a timing chart for a case in which the apparatuscollectively executes reset operation for a plurality of lines.

Note that the processing in steps S201 to S205, S207, and S208 in FIG.10A are the same as those in FIG. 2. The following description will bemainly focused on differences from the processing in FIG. 2.

If the apparatus determines in step S205 that X-ray irradiation iscomplete, the apparatus reads out the row number stored in the rownumber register 132 in step S1001. In step S1002, the apparatus performsread operation from the line corresponding to the row number next to therow number read in step S1001.

In the case shown in FIG. 11, since the apparatus has executed X-rayirradiation during execution of reset operation on the linecorresponding to row number=6, the apparatus performs read operationfrom the line corresponding to row number=7 which is the next rownumber, and stores each pixel digital value in a RAM 140. Setting theline next to the line on which reset operation has been executed duringX-ray irradiation as the line from which the apparatus starts readoperation in this manner can keep the time intervals from resetoperation to read operation on the respective lines constant. In thecase shown in FIG. 11, for example, a time interval t1 from resetoperation to read operation on the line corresponding to row number=5 isalmost equal to a time interval t2 from reset operation to readoperation on the line corresponding to row number=7.

Likewise, the processing in steps S201 to S205, S207, S501, and S208 inFIG. 10B is the same as that in FIG. 5, and hence a description of itwill be omitted. The following description will be mainly focused ondifferences from the processing in FIG. 5.

Upon determining in step S205 that the X-ray irradiation is complete,the apparatus reads out all the row numbers stored in the row numberregister 132 in step S1011. The apparatus then rearranges the read rownumbers according to a reset operation sequence and identifies thelatest row number in the reset operation sequence.

In the case shown in FIG. 12, the apparatus has performed resetoperation in the order of row numbers=1, 4, 7, 10, 3, 6, 9, 2, 5, and 8,and has performed X-ray irradiation during the execution of resetoperation on the lines corresponding to row numbers=3, 6, and 10. Forthis reason, the apparatus rearranges the row numbers of the lines onwhich reset operation has been executed when X-ray irradiation has beenexecuted into row numbers=10, 3, and 6 according to the reset operationsequence. As a result, the apparatus identifies “6” as the latest rownumber in the reset operation sequence.

Subsequently, in step S1012, the apparatus starts read operation fromthe line corresponding to the row number next to the row numberidentified in step S1011 (the line corresponding to the next row numberin the reset operation sequence).

In the case shown in FIG. 12, since the identified row number is “6” andthe reset operation sequence corresponds to row numbers=1, 4, 7, 10, 3,6, 9, 2, 5, and 8, the row number next to the identified row number “6”is “9”. The apparatus therefore starts read operation from the linecorresponding to row number=9 and performs read operation in the orderof row numbers=2, 5, 8, . . . .

When simultaneously performing reset operation on a plurality of lines,the apparatus sets, as the line from which it starts read operation, theline next to the latest line, of the lines on which reset operation hasbeen executed at the time of X-ray irradiation, in the reset operationsequence. This can keep the time intervals from reset operation to readoperation on the respective lines constant.

In the case shown in FIG. 12, for example, the time interval t1 fromreset operation to read operation on the line corresponding to rownumber=5 is almost equal to the time interval t2 from reset operation toread operation on the line corresponding to row number=7.

Fifth Embodiment

In each of the first to fourth embodiments, the apparatus is providedwith an X-ray detector 110 to detect whether X-rays have beenirradiated. The present invention is not limited to this. For example,the apparatus may be configured to detect, based on an output from atwo-dimensional sensor array 121 during the execution of resetoperation, whether X-rays have been irradiated. This embodiment will bedescribed in detail below.

<1. Arrangement of Radiation Imaging Apparatus>

The arrangement of a radiation imaging apparatus 1300 according to thefifth embodiment of the present invention will be described first. FIG.13 is a block diagram showing the arrangement of the radiation imagingapparatus 1300 according to the fifth embodiment of the presentinvention. The following description will be mainly focused ondifferences from the arrangement in FIG. 1.

The radiation imaging apparatus 1300 shown in FIG. 13 does not includethe X-ray detector 110. Instead of this, the apparatus is configured toalso transfer an output from an ADC (A/D Converter) 124 to a scancontrol signal generation circuit 131.

With this arrangement, the scan control signal generation circuit 131monitors the pixel digital value output from the ADC 124 during theexecution of reset operation, and can determine that X-rays have beenirradiated, when the pixel digital value abruptly increases. Note thatupon determining that X-rays have been irradiated, when the pixeldigital value on a line currently subjected to reset operation abruptlyincreases, the scan control signal generation circuit 131 performscontrol to continue the reset operation on the line. This makes itpossible to determine the completion of X-ray irradiation, when thepixel digital value on the line abruptly decreases afterward.

<2. Operation 1 of Radiation Imaging Apparatus>

The operation of the radiation imaging apparatus 1300 will be describednext with reference to FIGS. 14A and 15. FIG. 14A is a flowchart showinga procedure for imaging processing by the radiation imaging apparatus1300 which executes reset operation for each line. FIG. 15 is a timingchart for this procedure.

As shown in FIG. 14A, when starting imaging processing, the apparatusstarts reset operation for the two-dimensional sensor array 121 in stepS201. When starting reset operation, the apparatus sequentially performsreset operation from row number=1, as shown in FIG. 15, under thecontrol of a shift register 122. Upon performing reset operation up torow number=10, the apparatus performs reset operation again from rownumber=1.

During this period, in step S1401, the scan control signal generationcircuit 131 monitors a dark current on each line currently subjected toreset operation. If the scan control signal generation circuit 131determines in step S1401 that X-rays have been irradiated (YES in stepS202), the process advances to step S203. If a dark current hasincreased to a predetermined threshold or more, the scan control signalgeneration circuit 131 determines that X-rays have been irradiated. Upondetermining that no X-rays have been irradiated, the scan control signalgeneration circuit 131 continues to monitor a dark current on each lineon which reset operation has been performed.

In step S1402, the apparatus stores, in a row number register 132, therow number of a line on which reset operation has been executed upondetermining that X-rays have been executed. In step S1403, the apparatuscontinues reset operation on the line on which reset operation has beenexecuted upon determining that X-rays have been executed withoutperforming reset operation on the next line. This makes the apparatuscontinue to monitor a dark current on the line in step S1404.

If the apparatus determines the completion of X-ray irradiation (YES instep S205) as a result of monitoring of a dark current in step S1404,the process advances to step S205. When a dark current decreases by apredetermined threshold or more, the scan control signal generationcircuit 131 determines that X-ray irradiation is complete.

In the case shown in FIG. 15, when the dark current output from the linecorresponding to row number=6 abruptly increases during the execution ofreset operation at row number=6 (step S1501), the scan control signalgeneration circuit 131 determines that X-rays have been irradiated. Thismakes the scan control signal generation circuit 131 store the rownumber in the row number register 132, continue reset operation on theline corresponding to the row number, and continue to monitor a darkcurrent.

Upon detecting, as a result of monitoring a dark current, that the darkcurrent output from the line corresponding to row number=6 has abruptlydecreased (step S1502), the scan control signal generation circuit 131determines that X-ray irradiation is complete, and stops reset operationat row number=6 (step S1503).

Since the processing in steps S1001, S1002, S207, and S208 has alreadybeen described with reference to FIG. 2 or FIGS. 10A and 10B, adescription of it will be omitted hereinafter.

<3. Operation 2 of Radiation Imaging Apparatus>

Another operation of the radiation imaging apparatus 1300 will bedescribed next with reference to FIGS. 14B and 16. FIG. 14B is aflowchart showing a procedure for imaging processing by the radiationimaging apparatus 1300 which collectively executes reset operation on aplurality of lines. FIG. 16 is a timing chart for this procedure.

As shown in FIG. 14B, when starting imaging processing, the apparatusstarts reset operation for the two-dimensional sensor array 121 in stepS201. When starting reset operation, the apparatus sequentially performsreset operation in the order of row numbers=1, 4, 7, 10, 3, 6, 9, 2, 5,and 8, as shown in FIG. 16, under the control of the shift register 122.

During this period, in step S1411, the scan control signal generationcircuit 131 monitors a dark current on each line currently subjected toreset operation. If the scan control signal generation circuit 131determines in step S1411 that X-rays have been irradiated (YES in stepS202), the process advances to step S203. If a dark current hasincreased to a predetermined threshold or more, the scan control signalgeneration circuit 131 determines that X-rays have been irradiated. Upondetermining that no X-rays have been irradiated, the scan control signalgeneration circuit 131 continues to monitor a dark current on each lineon which reset operation has been performed.

In step S1412, the apparatus stores, in the row number register 132, therow numbers of all the lines on which reset operation has been executedupon determining that X-rays have been executed. In step S1413, theapparatus continues reset operation on all the lines on which resetoperation has been executed upon determining that X-rays have beenexecuted without performing reset operation on the next line. This makesthe apparatus continue to monitor dark currents on the plurality oflines in step S1414.

If the apparatus determines the completion of X-ray irradiation (YES instep S205) as a result of monitoring of dark currents in step S1414, theprocess advances to step S205. When a dark current on each linedecreases by a predetermined threshold or more, the scan control signalgeneration circuit 131 determines that X-ray irradiation is complete.

In the case shown in FIG. 16, when the dark currents output from thelines corresponding to row numbers=3, 6, and 10 abruptly increase duringthe execution of reset operation at row numbers=3, 6, and (step S1601),the scan control signal generation circuit 131 determines that X-rayshave been irradiated. This makes the scan control signal generationcircuit 131 store the row numbers in the row number register 132,continue reset operation on the lines corresponding to the row numbers,and continue to monitor dark currents.

Upon detecting, as a result of monitoring dark currents, that the darkcurrents output from the lines corresponding to row numbers=3, 6, and 10have abruptly decreased (step S1602), the scan control signal generationcircuit 131 determines that X-ray irradiation is complete, and stopsreset operation at row numbers=3, 6, 10 (steps S1603 to S1605).

Since the processing in steps S1011, S1012, S207, S501, and S208 hasalready been described with reference to FIG. 2, FIG. 5, and FIGS. 10Aand 10B, a description of it will be omitted hereinafter.

As is obvious from the above description, the radiation imagingapparatus 1300 according to this embodiment is configured to monitordark currents on lines currently subjected to reset operation and detectthe execution of X-ray irradiation based on changes in dark currents,instead of being provided with an X-ray detector. This apparatus isfurther configured to continue reset operation on lines subjected toreset operation when determining that X-rays have been irradiated andmonitor the completion of X-ray irradiation.

As a result, it is possible to obtain the same effects as those of thefirst to fourth embodiments without using any X-ray detector.

Sixth Embodiment

The fifth embodiment is configured to monitor outputs from the ADC 124to detect the execution of X-ray irradiation, instead of being providedwith the X-ray detector 110. However, the present invention is notlimited to this. For example, the apparatus may be configured to includea printed board capable of converting a current on a sensor bias line ofthe two-dimensional sensor array 121 into a voltage and outputting it asa digital value and monitor digital values output from the printed board(changes in the state of the two-dimensional sensor array 121).

The fifth embodiment described above is configured to determine thatX-rays have been irradiated, if a pixel digital value has abruptlyincreased. However, the present invention is not limited to this. Forexample, this apparatus may be configured to store a pixel digital valuein a state in which no X-rays are irradiated and determine whether X-rayirradiation has been performed, by comparison with the stored pixeldigital value.

FIG. 17 shows the arrangement of the two-dimensional sensor array 121according to this embodiment and its peripheral circuit. Thetwo-dimensional sensor array 121 includes a plurality of photoelectricconversion elements 1210 arranged in a matrix form and TFTs (Thin FilmTransistors) 1212 respectively coupled to the photoelectric conversionelements 1210. A power supply 1211 applies a bias voltage via a biasline connected to each photoelectric conversion element 1210. Thevoltage applied to a gate line 1213 commonly provided for each row ofthe TFTs 1212 controls conduction of each TFT 1212. Each gate line 1213is connected to the output side of a shift register 122 operating as adriving circuit, and receives an output from the shift register 122 tocontrol ON/OFF operation of each TFT 1212 on a row basis. The gate lines1213 respectively correspond to LINE 1 to LINE 10 in FIGS. 3, 6, 8, 11,12, 15, 16, 17, 20, 21, and 22. When the TFT 1212 is turned on, thecharge stored in the photoelectric conversion element 1210 is output viaa signal line 1214. A sample/hold circuit 1803 then holds it as anelectrical signal.

The photoelectric conversion elements 1210 of the two-dimensional sensorarray 121 may be so-called direct type elements which convert X-raysinto charges or may be elements which generate charges upon receivingvisible light. In this case, a phosphor which converts X-rays intovisible light is stacked on the two-dimensional sensor array 121.

The shift register 122 simultaneously addresses all the pixels on agiven row on the two-dimensional sensor array 121. The sample/holdcircuit 1803 then holds charges from the respective pixels on the row.The held charges output from the pixels are sequentially read via amultiplexer 1804. A charge amplifier 123 amplifies the charges. An A/Dconverter 143 then converts the charges into digital values. Every timescanning on each row is complete, the shift register 122 sequentiallydrives the next row on the sensor array. Finally, the charges outputfrom all the pixels are converted into digital values. This makes itpossible to read out radiation image data. In this case, the apparatusscans while fixing the voltage applied to each column signal line to aspecific value and discards acquired charges, thereby discharging darkcharges and performing scanning for the initialization of the sensor. Adriving control unit 220 including a scan control signal generationcircuit 131 of an ASIC 130 performs control such as driving and readoperation of the sensor unit.

The image data converted into digital values allows obtaining of acaptured image from which unnecessary dark charge components are removedby performing the offset correction of subtracting the offset image dataacquired from only the dark charge components without radiationirradiation from radiation image data.

FIG. 18 shows an example of the structure of the shift register 122according to the above embodiment. The shift register 122 includes aplurality of registers and AND gates connected to the output sides ofthe registers. The output sides of the respective registers areconnected to the DATA pins on the input sides of the registers adjacentto each other in a predetermined direction. The shift register 122includes a DATA pin which inputs data to the first register, a CLK pinwhich instructs all the registers to capture next data, an OE pin whichsimultaneously permits/inhibits outputs from all the registers, and aCLR pin which simultaneously clears the stored contents of all theregisters. The CLK and CLR pins are connected to the CLK and CLR inputportions of the respective registers. The DATA pin is connected to theDATA input portion of the first register. The DATA input portion of eachsucceeding register is connected to the output portion of theimmediately preceding register. The OE pin is connected to the AND gatesconnected to the respective registers. With this arrangement, therespective inputs to the CLK, CLR, and OE pins directly control thestate of all the registers or AND gates. Each input to the DATA pindirectly controls only the state of the first register. The scan controlsignal generation circuit 131 included in the driving control unit 220generates control signal inputs for the respective pins. An output fromeach AND gate is a digital value representing 0 or 1. Voltagesindicating such data values are connected as the outputs of the shiftregister to the respective gate lines 1213. Alternatively, amplificationunits provided for the respective AND gates perform predeterminedamplification of voltages indicating the respective digital values andoutput the amplified voltages. These output voltages include the firstvoltage which corresponds to digital value “1” and turns on the TFT 1212and the second voltage which digital value “0” and turns off the TFT1212.

Each register receives an input from the DATA pin and stores either thefirst data for turning on the TFTs 1212 on a corresponding row of thetwo-dimensional sensor array 121 or the second data for turning offthem. Controlling the CLK pin causes each register to capture the storedcontent of the adjacent register. That is, inputting one clock pulse tothe CLK pin can shift the selected state of each row of the TFTs 1212 byone row. Using the DATA and CLK pins in combination can select anarbitrary combination of rows of the two-dimensional sensor array 121.In addition, setting the OE pin in the OFF state can fix the output ofthe register to the OFF state regardless of the stored content. This canprevent any row of the two-dimensional sensor array 121 from beingunintentionally selected during shift operation.

A method of controlling the shift register 122 for the implementation ofreset scanning in FIG. 12 will be described with reference to FIG. 19.As described above, the selected state of each row is changed byinputting a clock pulse to the CLK pin. Since the skip count is three,clock pulses are input for every three rows to shift the selected state.The OE pin is switched to the OFF state so as not to select any rowwhich should not be selected during this shift operation. If a selectedrow is added near the head of the two-dimensional sensor array 121 asthe scan progresses, the DATA pin is controlled to satisfy this. Uponcompletion of the shift operation, the OE pin is switched to the ONstate to select a row of the two-dimensional sensor array 121.

As described above, one selection of each row in FIG. 12 is actuallyimplemented by a plurality of intermittent selections (three times of ONswitching and OFF switching in this case). However, since the durationof shift operation is sufficiently shorter than a selection period, aplurality of times of selection can be regarded as continuous operation.

The driving operation shown in FIG. 12 is executed in this manner. Inthe above case, TFTs are sequentially tuned on with a skip count ofthree, that is, for every two rows. However, the present invention isnot limited to this. Changing the skip count will implement the drivingoperation of sequentially turning on TFTs for every m (≧1) rows. Inaddition to reset scanning, the same operation is implemented insubsequent read scanning.

A radiation imaging apparatus according to another embodiment of thepresent invention will be described. This apparatus has the samestructure as that in the above embodiment, and differs from it only inthe method of scanning the two-dimensional sensor array 121. Therefore,only this point will be described.

In the first and second embodiments, every time the selected state of arow is switched, the selection of one row is canceled, and one row isadditionally selected. However, this operation is not essential to thepresent invention. A plurality of rows may be subjected to selectioncancellation and addition per switching operation or all selected rowsmay be simultaneously subjected to selection cancellation and addition.

This embodiment is configured to control the two-dimensional sensorarray 121 in consideration of this point. FIG. 20 shows thecorresponding operation. In the embodiment, skip count I=3 is set. Theembodiment differs from the second embodiment in that all simultaneouslyselected rows are simultaneously subjected to selection cancellation andaddition. Since reset periods are uniformly distributed on each row, thenumber of rows simultaneous selected at each moment in scanning variesin the range of 3 or 4. However, both the embodiments have the commonfeature that rows to be simultaneously selected are not adjacent to eachother. In reset scanning, selection of a plurality of rows issimultaneously started and ended. In contrast, in read scanning, rowsare selected one by one, and hence the periods during which darkcurrents are accumulated on the respective rows are not equal in astrict sense. However, it is possible to make a great improvement ascompared with the differences between accumulation periods in FIG. 2.

FIG. 21 shows control on the shift register 122, which implementsscanning in this embodiment. At an early stage in scanning, in order tosimultaneously start selecting a plurality of rows, many clocks and dataare input to the shift register 122 to turn on a plurality of registers,thereby setting an initial state. At this time, the state of skip countI=3 is implemented in the shift register 122. Controlling the OE pin inthis state will simultaneously ON/OFF-control the TFTs on a plurality ofrows. Since the skip selection state has already been set in the shiftregister 122, clock pulses for carrying on scanning may be input one byone to shift selected rows one by one. Only when the leading row isselected again as the scan progresses, a new ON signal is input to theDATA pin when inputting a clock.

Another radiation irradiation detection method can detect radiationirradiation by connecting, to a bias line connected to a power supply1211, a current measurement unit which monitors a current flowing on thebias line. When radiation is irradiated, the charge accumulated in aphotoelectric conversion elements 1210 in reset scanning is output via asignal line 1214, and charge flows on the bias line so as to compensatefor the output of the charge. Therefore, radiation irradiation isdetected by detecting a current on this bias line. The currentmeasurement unit is configured such that a resistor and an operationalamplifier are connected in parallel, the bias line is connected to theinput portion of the operational amplifier, and an amplification unitand an ADC are connected to the output portion of the operationalamplifier. The resistor performs DC voltage conversion. Theamplification unit amplifies this voltage. The ADC converts the voltageinto a digital value. The digital value is input to an FPGA operating asa comparator and is compared with a first digital threshold a in theFPGA. The FPGA periodically samples this voltage. When the voltagebecomes larger than the first digital threshold a, the FPGA determinesthat radiation irradiation has started.

Likewise, in combination with the driving operations shown in FIGS. 15and 16, it is also possible to determine the end of radiationirradiation. When determining the end of irradiation, after determiningthat radiation irradiation has started, the FPGA determines thatradiation irradiation has ended, when the voltage sampled by the FPGAbecomes smaller than a second digital threshold b.

The above-described embodiment of the present invention can improve theuser-friendliness of a radiation imaging apparatus configured to performthe reset operation of a sensor array.

Other Embodiments

Embodiments of the present invention can also be realized by a computerof a system or apparatus (or devices such as a CPU or MPU) that readsout and executes a program recorded on a memory device to perform thefunctions of the above-described embodiment(s), and by a method, thesteps of which are performed by a computer of a system or apparatus by,for example, reading out and executing a program recorded on a memorydevice to perform the functions of the above-described embodiment(s).For this purpose, the program is provided to the computer for examplevia a network or from a recording medium of various types serving as thememory device (for example, computer-readable medium).

While the embodiments of the present invention has been described withreference to exemplary embodiments, it is to be understood that theinvention is not limited to the disclosed exemplary embodiments. Thescope of the following claims is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures and functions.

This application claims the benefit of Japanese Patent Applications No.2012-128403 filed Jun. 5, 2012, and No. 2013-052433, filed Mar. 14,2013, which are hereby incorporated by reference herein in theirentirety.

What is claimed is:
 1. An X-ray radiation imaging apparatus including asensor array including a plurality of pixels arranged in a matrix form,a switch element connected to each pixel, and a column signal linecommon to pixels on each column to which each pixel is connected via theswitch element, the X-ray radiation imaging apparatus comprising: afirst control unit configured to control reset operation of sequentiallyremoving signals respectively output from a plurality of linesconstituting the sensor array; an identifying unit configured toidentify a line currently subjected to the reset operation when a startof X-ray radiation irradiation is detected; a second control unitconfigured to control read operation of reading a signal output fromeach of the plurality of lines at a timing set in advance for each lineupon completion of the X-ray radiation irradiation; an interpolationunit configured to interpolate an image, which is part of an imagegenerated based on signals read by the read operation, and whichcorresponds to a line identified by the identifying unit, by usingimages of adjacent lines; a driving circuit which performs control toset the switch element in an ON state and an OFF state for each row; anda detection unit configured to detect X-ray radiation irradiation bymonitoring an electrical signal output from the pixel, wherein the firstcontrol unit controls the driving circuit to set a switch element oneach row in an ON state for a predetermined period, wherein, with afirst row, a second row, a third row, and a fourth row arranged in theorder named, the first control unit performs control to set switchelements on the first and third rows in an ON state while setting switchelements on the second and fourth rows in an OFF state in a first periodand to set switch elements on the second and fourth rows in an ON statewhile setting the switch elements on the first and third rows in an OFFstate in a second period which does not overlap the first period, andwherein the first control unit causes the switch element on a row whichis in an ON state when the detection circuit has detected X-rayradiation irradiation to continue an ON state for a period longer thanthe predetermined period.
 2. The apparatus according to claim 1, whereinthe first control unit controls a timing of removal of a signal outputfrom each of the plurality of lines so as to perform the reset operationfor every n lines (n being an integer ≧2).
 3. The apparatus according toclaim 2, wherein the first control unit controls the timing so as tosatisfy a relation n=N/S where S (S being an integer ≧2) is the numberof lines on which timings of the reset operation overlap and N is thenumber of lines constituting the sensor array (and N being an integer≧2).
 4. The apparatus according to claim 1, wherein the second controlunit performs control to start the read operation from a line next tothe line identified by the identifying unit.
 5. The apparatus accordingto claim 4, wherein the second control unit performs control to startthe read operation from a line next to a latest line in a sequence ofthe reset operation when the identifying unit identifies a plurality oflines.
 6. The apparatus according to claim 1, wherein the identifyingunit identifies a line currently subjected to the reset operation whenthe detection unit detects the X-ray radiation irradiation.
 7. Theapparatus according to claim 6, wherein the detection unit detects theX-ray radiation irradiation based on a change in a state of the sensorarray.
 8. The apparatus according to claim 1, further comprising amonitoring unit configured to monitor a signal output from each line inthe reset operation, wherein the identifying unit identifies a linecurrently subjected to the reset operation when it is determined, basedon a change in the signal monitored by the monitoring unit, that theX-ray radiation has been irradiated.
 9. The apparatus according to claim8, wherein the second control unit starts the read operation when it isdetermined, based on a change in the signal monitored by the monitoringunit, that the X-ray radiation irradiation is complete.
 10. Theapparatus according to claim 1, wherein the first control unit causesthe driving circuit to set a switch element on each row in an ON statefor a predetermined period so as to simultaneously set the switchelements on a plurality of rows in an ON state while inhibiting theswitch elements on adjacent rows from being simultaneously set in an ONstate.
 11. The apparatus according to claim 1, wherein the first controlunit performs control to sequentially set the switch elements on everym^(th) row (m being ≧1), for every predetermined number of switchelements.
 12. The apparatus according to claim 1, wherein the firstcontrol unit sequentially performs control to sequentially set theswitch elements on odd-numbered rows in an ON state, for everypredetermined number of switch elements, and control to sequentially setthe switch elements on even-numbered rows in an ON state, for everypredetermined number of switch elements.
 13. The apparatus according toclaim 1, further comprising a specifying unit configured to specify anumber of a row which is in an ON state when the detection circuit hasdetected X-ray radiation irradiation.
 14. The apparatus according toclaim 13, further comprising a correction unit configured to correctimage data corresponding to at least the specified row based on imagedata corresponding to rows adjacent to the specified row.
 15. Theapparatus according to claim 1, wherein the detection circuit furtherdetects an end of X-ray radiation irradiation based on an electricalsignal from a row corresponding to the switch element caused to continuethe ON state.
 16. The apparatus according to claim 15, wherein the firstcontrol unit shifts the switch element on the row which is caused tocontinue the ON state to an OFF state when an end of the X-ray radiationirradiation is detected.
 17. The apparatus according to claim 1, furthercomprising a reading circuit which reads an electrical signal outputfrom each pixel to the column signal line when a switch element on theeach row is set in an ON state, wherein the first control unit obtainsimage data by causing the reading circuit to read electrical signalsobtained by setting switch elements on the each row in an OFF state inaccordance with detection of X-ray radiation irradiation by thedetection circuit and sequentially setting switch elements on the eachrow in an ON state after a lapse of a predetermined period.
 18. Theapparatus according to claim 17, wherein the first control unitterminates an ON state of the switch element on the row which is in anON state when the detection circuit has detected X-ray radiationirradiation in accordance with detection of the X-ray radiationirradiation even before the lapse of the predetermined period.
 19. Theapparatus according to claim 17, wherein the first control unit performscontrol such that the predetermined period, during which the switchelement is in ON state before detection of X-ray radiation by thedetection circuit, is longer than a period during which the switchelement is in an ON state when the image data is obtained.
 20. Theapparatus according to claim 1, wherein the first control unitsequentially shifts switch elements on each row to an ON state such thata period during which a given row is in an ON state overlaps a periodduring which another row is in an ON state for a period shorter than theperiod during which the given row is in an ON state.
 21. The apparatusaccording to claim 1, wherein the driving circuit sets a switch elementon the first row in an OFF state for a predetermined period between afirst period overlapping a period, of a period during which a switchelement on the first row is in an ON state, during which a switchelement on the third row is in an ON state, and a second period whichdoes not overlap a period, of the period during which the switch elementon the first row is in an ON state, during which the switch element onthe third row is in an ON state.
 22. A method of controlling an X-rayradiation imaging apparatus including a sensor array including aplurality of pixels arranged in a matrix form, a switch elementconnected to each pixel, and a column signal line common to pixels oneach column to which each pixel is connected via the switch element, anda driving circuit which performs control to set the switch element in anON state and an OFF state for each row, and a detection unit configuredto detect X-ray radiation irradiation by monitoring an electrical signaloutput from the pixel, the method comprising: a first control step ofcontrolling reset operation of sequentially removing signalsrespectively output from a plurality of lines constituting the sensorarray; an identifying step of identifying a line currently subjected tothe reset operation when a start of X-ray radiation irradiation isdetected; a second control step of controlling read operation of readinga signal output from each of the plurality of lines at a timing set inadvance for each line upon completion of the X-ray radiationirradiation; and an interpolation step of interpolating an image, whichis part of an image generated based on signals read by the readoperation, and which corresponds to a line identified in the identifyingstep, by using images of adjacent lines, wherein, in the first controlstep, control of the driving circuit is executed to set a switch elementon each row in an ON state for a predetermined period, wherein with afirst row, a second row, a third row, and a fourth row arranged in theorder named, in the first control step, control is executed to setswitch elements on the first and third rows in an ON state while settingswitch elements on the second and fourth rows in an OFF state in a firstperiod and to set the switch elements on the second and fourth rows inan ON state while setting the switch elements on the first and thirdrows in an OFF state in a second period which does not overlap the firstperiod, and wherein in the first control step, the switch element on arow which is in an ON state when the detection circuit has detectedX-ray radiation irradiation is caused to continue the ON state for aperiod longer than the predetermined period.
 23. A non-transitorycomputer-readable storage medium storing a program for causing acomputer to execute steps in a method of controlling an X-ray radiationimaging apparatus including a sensor array including a plurality ofpixels arranged in a matrix form, a switch element connected to eachpixel, and a column signal line common to pixels on each column to whicheach pixel is connected via the switch element, and a driving circuitwhich performs control to set the switch element in an ON state and anOFF state for each row, and a detection unit configured to detect X-rayradiation irradiation by monitoring an electrical signal output from thepixel, the method comprising: a first control step of controlling resetoperation of sequentially removing signals respectively output from aplurality of lines constituting the sensor array; an identifying step ofidentifying a line currently subjected to the reset operation when astart of X-ray radiation irradiation is detected; a second control stepof controlling read operation of reading a signal output from each ofthe plurality of lines at a timing set in advance for each line uponcompletion of the X-ray radiation irradiation; and an interpolation stepof interpolating an image, which is part of an image generated based onsignals read by the read operation, and which corresponds to a lineidentified in the identifying step, by using images of adjacent lines,wherein, in the first control step, control of the driving circuit isexecuted to set a switch element on each row in an ON state for apredetermined period, wherein with a first row, a second row, a thirdrow, and a fourth row arranged in the order named, in the first controlstep, control is executed to set switch elements on the first and thirdrows in an ON state while setting switch elements on the second andfourth rows in an OFF state in a first period and to set the switchelements on the second and fourth rows in an ON state while setting theswitch elements on the first and third rows in an OFF state in a secondperiod which does not overlap the first period, and wherein in the firstcontrol step, the switch element on a row which is in an ON state whenthe detection circuit has detected X-ray radiation irradiation is causedto continue the ON state for a period longer than the predeterminedperiod.
 24. An X-ray radiation imaging apparatus comprising: an imagingunit including a plurality of pixels arranged in a matrix form, a switchelement connected to each pixel, and a column signal line common topixels on each column to which each pixel is connected via the switchelement; a driving circuit which performs control to set the switchelement in an ON state and an OFF state for each row; a control unitwhich causes the driving circuit to set a switch element on each row inan ON state for a predetermined period so as to simultaneously set theswitch elements on a plurality of rows in an ON state while inhibitingthe switch elements on adjacent rows from being simultaneously set in anON state; and a detection circuit which detects X-ray radiationirradiation by monitoring an electrical signal output from the pixel bythe control, wherein the control unit causes the switch element on a rowwhich is in an ON state when the detection circuit has detected X-rayradiation irradiation to continue an ON state for a period longer thanthe predetermined period.
 25. An X-ray radiation imaging apparatuscomprising: an imaging unit including a plurality of pixels arranged ina matrix form, a switch element connected to each pixel, and a columnsignal line common to pixels on each column to which each pixel isconnected via the switch element; a driving circuit which performscontrol to set the switch element in an ON state and an OFF state foreach row; a control unit configured to control the driving circuit toset a switch element on each row in an ON state for a predeterminedperiod; and a detection circuit which detects X-ray radiationirradiation by monitoring an electrical signal output from the pixel bythe control, and detects an end of X-ray radiation irradiation based onan image signal from a row corresponding to the switch element caused tocontinue the ON state, wherein, with a first row, a second row, a thirdrow, and a fourth row arranged in the order named, the control unitexecutes control to set switch elements on the first and third rows inan ON state while setting switch elements on the second and fourth rowsin an OFF state in a first period and set the switch elements on thesecond and fourth rows in an ON state while setting the switch elementson the first and third rows in an OFF state in a second period whichdoes not overlap the first period, and the control unit further causesthe switch element on the row which is in an ON state when the detectioncircuit has detected X-ray radiation irradiation to continue the ONstate for a period longer than the predetermined period, and shifts theswitch element on the row caused to continue the ON state when an end ofthe X-ray radiation irradiation is detected to an OFF state.
 26. AnX-ray radiation imaging system comprising: an X-ray irradiation unitwhich irradiates X-ray radiation; an imaging unit including a pluralityof pixels arranged in a matrix form, a switch element connected to eachpixel, and a column signal line common to pixels on each column to whicheach pixel is connected via the switch element; a driving circuit whichperforms control to set the switch element in an ON state and an OFFstate for each row; a control unit which causes the driving circuit toset a switch element on each row in an ON state for a predeterminedperiod so as to simultaneously set the switch elements on a plurality ofrows in an ON state while inhibiting the switch elements on adjacentrows from being simultaneously set in an ON state; and a detectioncircuit which detects X-ray radiation irradiation by monitoring anelectrical signal output from the pixel by the control, wherein thecontrol unit causes the switch element on a row which is in an ON statewhen the detection circuit has detected X-ray radiation irradiation tocontinue an ON state for a period longer than the predetermined period.27. An X-ray radiation imaging system comprising: an X-ray irradiationunit which irradiates X-ray radiation; an imaging unit including aplurality of pixels arranged in a matrix form, a switch elementconnected to each pixel, and a column signal line common to pixels oneach column to which each pixel is connected via the switch element; adriving circuit which performs control to set the switch element in anON state and an OFF state for each row; a control unit configured tocause the driving circuit to set a switch element on each row in an ONstate for a predetermined period; a detection circuit which detectsX-ray radiation irradiation by monitoring an electrical signal outputfrom the pixel by the control, and detects an end of X-ray radiationirradiation based on an image signal from a row corresponding to theswitch element caused to continue the ON state, wherein, with a firstrow, a second row, a third row, and a fourth row arranged in the ordernamed, the control unit executes control to set switch elements on thefirst and third rows in an ON state while setting switch elements on thesecond and fourth rows in an OFF state in a first period and set theswitch elements on the second and fourth rows in an ON state whilesetting the switch elements on the first and third rows in an OFF statein a second period which does not overlap the first period, and thecontrol unit further causes the switch element on the row which is in anON state when the detection circuit has detected X-ray radiationirradiation to continue the ON state for a period longer than thepredetermined period, and shifts the switch element on the row caused tocontinue the ON state when an end of the X-ray radiation irradiation isdetected to an OFF state.
 28. A method of controlling an X-ray radiationimaging apparatus including an imaging unit including a plurality ofpixels arranged in a matrix form, a switch element connected to eachpixel, and a column signal line common to pixels on each column to whicheach pixel is connected via the switch element, and a driving circuitwhich performs control to set the switch element in an ON state and anOFF state for each row, and a detection unit configured to detect X-rayradiation irradiation by monitoring an electrical signal output from thepixel, the method comprising: a control step of causing the drivingcircuit to set a switch element on each row in an ON state for apredetermined period so as to simultaneously set the switch elements ona plurality of rows in an ON state while inhibiting the switch elementson adjacent rows from being simultaneously set in an ON state; and adetection step of detecting X-ray radiation irradiation by monitoring anelectrical signal output from the pixel by the control, wherein in thecontrol step, the switch element on a row which is in an ON state whenthe detection circuit has detected X-ray radiation irradiation is causedto continue the ON state for a period longer than the predeterminedperiod.
 29. A method of controlling an X-ray radiation imaging apparatusincluding an imaging unit including a plurality of pixels arranged in amatrix form, a switch element connected to each pixel, and a columnsignal line common to pixels on each column to which each pixel isconnected via the switch element, and a driving circuit which performscontrol to set the switch element in an ON state and an OFF state foreach row, comprising: a control step of controlling the driving circuitto set a switch element on each row in an ON state for a predeterminedperiod; and a detection step of detecting X-ray radiation irradiation bymonitoring an electrical signal output from the pixel by the control,and detecting an end of X-ray radiation irradiation based on an imagesignal from a row corresponding to the switch element caused to continuethe ON state, wherein with a first row, a second row, a third row, and afourth row arranged in the order named, in the control step, control isexecuted to set switch elements on the first and third rows in an ONstate while setting switch elements on the second and fourth rows in anOFF state in a first period and set the switch elements on the secondand fourth rows in an ON state while setting the switch elements on thefirst and third rows in an OFF state in a second period which does notoverlap the first period, and in the control step, the switch element onthe row which is in an ON state when the detection circuit has detectedX-ray radiation irradiation is caused to continue the ON state for aperiod longer than the predetermined period, and the switch element onthe row caused to continue the ON state when an end of the X-rayradiation irradiation is detected is shifted to an OFF state.
 30. Anon-transitory computer-readable storage medium storing a program forcausing a computer to execute steps in a method of controlling an X-rayradiation imaging apparatus including an imaging unit including aplurality of pixels arranged in a matrix form, a switch elementconnected to each pixel, and a column signal line common to pixels oneach column to which each pixel is connected via the switch element, anda driving circuit which performs control to set the switch element in anON state and an OFF state for each row, and a detection unit configuredto detect X-ray radiation irradiation by monitoring an electrical signaloutput from the pixel, the method comprising: a control step of causingthe driving circuit to set a switch element on each row in an ON statefor a predetermined period so as to simultaneously set the switchelements on a plurality of rows in an ON state while inhibiting theswitch elements on adjacent rows from being simultaneously set in an ONstate; and a detection step of detecting X-ray radiation irradiation bymonitoring an electrical signal output from the pixel by the control,wherein in the control step, the switch element on a row which is in anON state when the detection circuit has detected X-ray radiationirradiation is caused to continue the ON state for a period longer thanthe predetermined period.
 31. A non-transitory computer-readable storagemedium storing a program for causing a computer to execute steps in amethod of controlling an X-ray radiation imaging apparatus including animaging unit including a plurality of pixels arranged in a matrix form,a switch element connected to each pixel, and a column signal linecommon to pixels on each column to which each pixel is connected via theswitch element, and a driving circuit which performs control to set theswitch element in an ON state and an OFF state for each row, comprising:a control step of controlling the driving circuit to set a switchelement on each row in an ON state for a predetermined period; and adetection step of detecting X-ray radiation irradiation by monitoring anelectrical signal output from the pixel by the control, and detecting anend of X-ray radiation irradiation based on an image signal from a rowcorresponding to the switch element caused to continue the ON state,wherein with a first row, a second row, a third row, and a fourth rowarranged in the order named, in the control step, control is executed toset switch elements on the first and third rows in an ON state whilesetting switch elements on the second and fourth rows in an OFF state ina first period and set the switch elements on the second and fourth rowsin an ON state while setting the switch elements on the first and thirdrows in an OFF state in a second period which does not overlap the firstperiod, and in the control step, the switch element on the row which isin an ON state when the detection circuit has detected X-ray radiationirradiation is caused to continue the ON state for a period longer thanthe predetermined period, and the switch element on the row caused tocontinue the ON state when an end of the X-ray radiation irradiation isdetected is shifted to an OFF state.